Allen Weisselberg, who's been described as a person who knows where "the bodies are buried," has been granted immunity by federal prosecutors after testifying against Donald Trump in the ongoing probe of lawyer Michael Cohen.

Weisselberg has been Chief Financial Officer of the Trump Organization since 2000. He's said to have revealed incriminating information about Trump's illegal dealings that involved the participation of the Trump Organization.

Weisselberg has worked for the Trump and his father, Fred, for decades. When Trump became president of the Trump Organization, he handed over the day-to-day control of the business to his two elder sons and Weisselberg. Weisselberg is also the person who prepares Trump's annual tax returns.

The only other two people who know as much about the Trump Organization's convoluted financial dealings is Trump himself, and his son, Donald Jr.

Weisselberg was subpoenaed in July to testify before a federal grand jury regarding the Cohen investigation. He was granted immunity in exchange for giving prosecutors information dealing with the investigation into Cohen and the hush money payments Cohen made to women during the 2016 presidential campaign.

Weisselberg made possible for the Trump Organization to compensate Cohen a $35,000 monthly retainer fee following Cohen's money payments to adult film actress Stormy Daniels to prevent her from disclosing information.

Weisselberg's testimony should prove the most damaging to Trump, who continues to be investigated by Special Counsel Robert Mueller. It's now clearly obvious Mueller is following the money in his investigation into meddling by the Russians in the 2016 presidential election.

Weisselberg "knows where all the bodies are buried," according to one lawyer. Other legal experts pointed out the only reason federal authorities would grant immunity to Weisselberg is if they were really targeting Trump and needed Weisselberg to make those charges stick.

Mueller is also taking down one-by-one members of Trump's inner circle, such as Cohen and Paul Manafort, as he turns the screws on Trump.

Weisselberg's cooperation is the latest twist in the prosecution of Cohen by the United States Attorney for the Southern District of New York. The investigation of Cohen began on a raid in his Manhattan home in April. On Aug. 21, Cohen pleaded guilty to eight federal charges, implicating Trump in those crimes.